Working with highly talented group of people. The company's name has a lot of weight and looks good on your resume. It's a very diverse company.
Cons
Contractor beware. I was brought on as a contract-to-hire. Three months in T. Rowe announced they were freezing hiring, but they extended my contract regardless. A year later they announced they weren't extending contractors except in extraordinary circumstances. When I started I was the the third contractor on my team and when I left my team had no contractors left. So whatever they promise you to get in the door, take with a grain of salt. Also be forewarned: contractors will be furloughed over the Winter holidays, that's three weeks of pay you'll lose.
I've contracted elsewhere in my career and T Rowe stands out for how contractors are second class employees. Besides furloughs you won't be able to attend many meetings or get training. Meanwhile you'll have to adhere to the same strict scrutiny as a regular employee: the company will monitor your stock transactions and prevent you from participating in all sorts of outside activities.